LED retrofit festoon bulbs are known that include a rigid circuit board that is equipped with multiple light diodes (LEDs). In each case, a festoon bulb contact is attached to the circuit board at two opposite lying ends. The circuit board can be surrounded for protection purposes by a transparent tube, wherein the tube is held at the end side by the festoon contacts. A driver is provided either on the circuit board or is accommodated in one of the festoon contacts. In the case of these LED retrofit festoon lamps, the problem arises that heat generated by the LEDs can only be discharged in a less than effective manner and as a result the output of the LEDs is limited.